5728-46-1Relevant articles and documents
Understanding the remarkable difference in liquid crystal behaviour between secondary and tertiary amides: The synthesis and characterisation of new benzanilide-based liquid crystal dimers
Strachan, Grant J.,Harrison, William T. A.,Storey, John M. D.,Imrie, Corrie T.
, p. 12600 - 12611 (2021)
A number of liquid crystal dimers have been synthesised and characterised containing secondary or tertiary (N-methyl) benzanilide-based mesogenic groups. The secondary amides all form nematic phases, and we present the first example of an amide to show the twist-bend nematic (NTB) phase. Only two of the correspondingN-methylated dimers formed a nematic phase and with greatly reduced nematic-isotropic transition temperatures. Characterisation using 2D ROESY NMR experiments, DFT geometry optimisation and X-ray diffraction reveal that there is a change in the preferred conformation of the benzanilide core on methylation, fromZtoE. The rotational barrier around the N-C(O) bond has been measured using variable temperature1H NMR spectroscopy. This dramatic change in shape accounts for the remarkable difference in liquid crystalline behaviour between these secondary and tertiary amide-based materials.
Amplification of Elementary Surface Reaction Steps on Transition Metal Surfaces Using Liquid Crystals: Dissociative Adsorption and Dehydrogenation
Yu, Huaizhe,Szilvási, Tibor,Wang, Kunlun,Gold, Jake I.,Bao, Nanqi,Twieg, Robert J.,Mavrikakis, Manos,Abbott, Nicholas L.
, p. 16003 - 16013 (2019)
Elementary reaction steps, including adsorption and dissociation, of a range of molecular adsorbates on transition metal surfaces have been elucidated in the context of chemical catalysis. Here we leverage this knowledge to design liquid crystals (LCs) supported on ultrathin polycrystalline gold films (predominant crystallographic face is (111)) that are triggered to undergo orientational transitions by dissociative adsorption and dehydrogenation reactions involving chlorine and carboxylic acids, respectively, thus amplifying these atomic-scale surface processes in situ into macroscopic optical signals. We use electronic structure calculations to predict that 4′-n-pentyl-4-biphenylcarbonitrile (5CB), a room temperature nematic LC, does not bind to Au(111) in an orientation that changes upon dissociative adsorption of molecular chlorine, a result validated by experiments. In contrast, 4-cyano-4-biphenylcarboxylic acid (CBCA) is calculated to bind strongly to Au(111) in a perpendicular orientation via dehydrogenation of the carboxylic acid group, which we confirmed using polarization-modulation infrared reflection-absorption spectroscopy. A maximum coverage of 0.07 monolayer of CBCA on the gold surface is sufficient to cause a perpendicular orientation of the LC. Dissociative adsorption of Cl2 gas on the gold surface, resulting in 0.5 monolayer coverage of Cl, displaces CBCA from Au(111) and thus triggers a strikingly visible change in orientation of the LC. Infrared spectroscopy established the orientation of adsorbed CBCA to be parallel to the Cl covered surface, with the COOH plane perpendicular to the surface, as predicted by first-principles calculations. These results demonstrate the use of first-principles calculations and transition metal surfaces to design LCs that report in situ targeted atomic-scale surface processes.
Thioether-linked liquid crystal dimers and trimers: The twist-bend nematic phase
Arakawa, Yuki,Komatsu, Kenta,Inui, Satoyoshi,Tsuji, Hideto
, (2019/09/10)
Systematic synthesis of thioether-linked dimers and trimers was carried out to reveal molecular designs for inducing mesophases and twist-bend nematic (NTB) phases. A five-fold approach based on molecular structural parameters including the ter
Palladium-catalyzed decarbonylative Suzuki-Miyaura cross-coupling of amides by carbon-nitrogen bond activation
Zhou, Tongliang,Ji, Chong-Lei,Hong, Xin,Szostak, Michal
, p. 9865 - 9871 (2019/11/11)
Palladium-catalyzed Suzuki-Miyaura cross-coupling or aryl halides is widely employed in the synthesis of many important molecules in synthetic chemistry, including pharmaceuticals, polymers and functional materials. Herein, we disclose the first palladium-catalyzed decarbonylative Suzuki-Miyaura cross-coupling of amides for the synthesis of biaryls through the selective activation of the N-C(O) bond of amides. This new method relies on the precise sequence engineering of the catalytic cycle, wherein decarbonylation occurs prior to the transmetallation step. The reaction is compatible with a wide range of boronic acids and amides, providing valuable biaryls in high yields (>60 examples). DFT studies support a mechanism involving oxidative addition, decarbonylation and transmetallation and provide insight into high N-C(O) bond activation selectivity. Most crucially, the reaction establishes the use of palladium catalysis in the biaryl Suzuki-Miyaura cross-coupling of the amide bond and should enable the design of a wide variety of cross-coupling methods in which palladium rivals the traditional biaryl synthesis from aryl halides and pseudohalides.